The official, speaking on condition of anonymity because he was not allowed to talk publicly to the media, gave no further details.

The"terrorist" bombing rocked Damascus on Friday causing casualties among civilians and the security forces, state media reported, barely a fortnight after two suicide bombers killed 44 people in the Syrian capital.

The "powerful explosion" struck in the Midan neighbourhood in the heart of the city, state television said.

"The attack took place in a heavily populated working-class neighbourhood near a school" and "killed and wounded dozens of people," said the state television. It showed gruesome footage of rescuers gathering body parts in the streets and placing them in plastic trash bags, in an area where damaged cars and buses could be seen splattered with blood.

Angry residents were at the scene shouting and denouncing the bombing as the work of "terrorists".

SANA news agency spoke of casualties among both civilians and security force personnel and the wail of ambulance sirens was heard in the city centre.

The December 23 bombings sparked a swirl of claims and counter-claims over who was responsible, with the authorities saying they were likely the work of Al-Qaeda and the opposition pointing the finger at the regime.

The latest blast came ahead of planned mass protests by pro-democracy activists to demand that an Arab League observer mission in Syria for two weeks acknowledge its failure to stem nearly 10 months of bloodshed and hand over to the United Nations.